1. Field of the Invention
The invention relates to a low temperature-fired porcelain and an electronic part using the porcelain.
2. Related Art Statement
A laminate type dielectric filter has been used as a high frequency circuit filter, such as a top filter, interstage filter for transmission, local filter and interstage filter for reception, in a high frequency circuit radio instrument such as a cellular phone. Examples of such laminate type dielectric filters are disclosed, for example, in a publication JP-A-243810/1993.
The laminate type dielectric filter may be produced as follows. Ceramic powder for producing a dielectric material is shaped to provide a plurality of green sheets. A given conductive paste is printed on each green sheet to form a conductive paste layer with a predetermined electrode pattern on each green sheet. The obtained green sheets are then laminated to form a laminated body. The laminated body is then heated so that the green sheets and conductive paste layers are simultaneously sintered and densified.
The electrode is generally made of a metallic conductor with a low melting point, such as a silver-based conductor, copper-based conductor or nickel-based conductor. Such metallic conductor has a low melting point, for example, of not higher than 1100° C. and sometimes as low as around 930° C. It is therefore necessary to fire the laminate body at a firing temperature lower than the melting point of the metal constituting the electrode pattern.
It has been desired to provide a porcelain with a low optimum firing temperature (low temperature-fired porcelain) having a reduced dielectric constant εr and improved quality coefficient Q. Such porcelain is indispensable for reducing the stray capacity, delay time and high frequency loss of a resonator and condenser housed. The assignee or applicant filed a Japanese Patent publication JP 211,969/2000A, and disclosed a low temperature fired porcelain with a optimum firing temperature not higher than 1000° C., a dielectric constant of not higher than 10 and a quality coefficient Q of not higher than 2500. This is a porcelain of silica-alumina-barium oxide system, in which celsian phase of a high strength is precipitated.